7th grade · Math · Unit 18 of 22
Two-Step Equations
Undo, undo, solve for x
What your child practices
Solving equations like 3x + 5 = 26 by undoing each step on both sides, writing equations from word problems and checking solutions.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 7.10(A); 7.11(A) · writing and solving two-step equations
How we explain it
Children can open this short lesson before they practice.
- Keep the equation balanced: do the same to both sides.
- Undo the adding or subtracting first.
- Then undo the multiplying or dividing.
Example: 2x + 3 = 11 Subtract 3 from both sides: 2x = 8. Divide both sides by 2: x = 4. Answer: x = 4
Two-Step Equations in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 18 of 22 in 7th grade Math, after Linear Relations and before Algebra Moves.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Texas Education Agency (TEA)
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
To solve 3x + 20 = 59, how do you undo the + 20?
- Subtract 20 from both sides
- Divide both sides by 20
- Subtract 20 from the left side only
- Add 20 to both sides
Subtract 20 from both sides
Hint: Use the opposite operation, and keep the equation balanced by doing it to both sides. The opposite of adding 20 is subtracting 20.
Question 2
Solve for x.
5x + 30 = 70
answer box
8
Hint: Undo the + 30 first: subtract 30 from both sides to get 5x = 40. Then undo the × 5: divide both sides by 5 to get x = 8.
Question 3
Solve: 7n − 21 = 49
- 4
- 28
- 70
- 10
10
Hint: Undo the − 21 first: add 21 to both sides to get 7n = 70. Then divide both sides by 7: n = 10.
Question 4
On a balance scale, 8 identical bags of marbles plus 14 loose marbles balance 54 loose marbles. How many marbles are in each bag?
⚖️8x + 14 = 54answer box
5
Hint: Take 14 marbles off both sides: 8 bags balance 40 marbles. Share them among 8 bags: 40 ÷ 8 = 5.
Question 5
Solve for x.
30 = 3x + 12
answer box
6
Hint: The x can be on either side. Subtract 12 on both sides: 18 = 3x. Then divide by 3: x = 6.
Question 6
Which equation matches this sentence? "Two times a number, minus 6, equals 14."
- 2(n − 6) = 14
- 6n − 2 = 14
- 2n − 6 = 14
- 2n + 6 = 14
2n − 6 = 14
Hint: "Two times a number" is 2n. "Minus 6" subtracts 6 after multiplying: 2n − 6. "Equals 14" finishes it: 2n − 6 = 14.